With the growing popularity of using the Internet to transfer files in digital format, there has been increasing concern over the need to protect the intellectual property rights of individuals and organizations to copyrighted materials such as books, music, movies and manuscripts. Once copyrighted materials have been made available in digital format, high quality illegal copies of copyrighted materials can be quickly and indiscriminately be made available to others.
Several web sites currently make available, for free distribution, unencrypted files of the contents of copyrightable material, such as books and audio music. Several of these web sites are maintained with the full consent of the lawful owners of the copyrighted material because some copyright owners see this as a way to help promote and market their products. On the other hand, there are other web sites that make available copyrighted files without the consent of the rightful owners of the copyright. Generally, it is desirable to allow web sites to distribute lawfully available copies of both unencrypted and encrypted files over the Internet to digital devices while concurrently preventing these digital devices from being able to either play or download illegally available files. One technique that is currently used to address this problem uses encryption to allow only devices with the appropriate encryption key to decrypt a particular file; therefore, when an encrypted file is downloaded from a web site, only the devices for which the file was intended are able to decrypt that file.
Existing encryption techniques are appropriate in the situation where only legal sources have access to specific copyrighted material and precaution has been made to assure that whoever downloads that material cannot subsequently distribute the material in an unencrypted format for use, by way of example, on another device able to display, reproduce or play the copyrighted material. I have noticed however, that existing encryption methods do not solve the problem of protecting copyrighted material from unlawful use or reproduction if the copyrighted material is already available in the hands of those who would make it available illegally; such is the case with music files, which are already widely distributed in digital format (i.e., compact discs, commonly known as “CD's”) making it easy for someone to illegally distribute the musical content read from the disc over the Internet.
The fact that the digital content of a file, such as music, happens to be encrypted does not mean that the digital content has been made available with the consent of the rightful owners in the first place; therefore, encryption alone is not sufficient to address this problem of protecting copyrightable material.
One solution recently proposed to address this problem suggests that each file be encoded with a digital signature whereby PC's and other devices can recognize that only files with that type of digital signature are legal. I have noticed that one problem with this approach is that, although an attempt may be made to limit the distribution of the digital signature algorithm generator, it may be difficult to keep the generator from reaching the hands of those who would put digital signatures on files which are distributed without the authorization of the rightful owners of those files; once the digital signature generator is in unauthorized hands, reliance upon the generator becomes useless as a method for differentiating between legally and illegally copied files.